Vanuatu’s currency is the vatu (VT), which floats against a basket of currencies including the US dollar, so it is reasonably stable. It’s easy to exchange Australian dollars and most major currencies in main banks.
Commercial banks in Vanuatu are ANZ (http://anz.com/vanuatu), Westpac (http://westpac.vu), the local National Bank of Vanuatu (NBV) and the French bank Bred (www.bred.vu).
Banks have offices in central Port Vila and branches in Luganville on Santo. ANZ and Westpac have plenty of ATMs in Port Vila, and a couple each in Luganville. There are ATMs at the international airports in Santo and Port Vila.
Exchange rates between vary and you'll invariably be slugged with a fee at both ends, so it pays to use ATMs sparingly. The maximum you can withdraw is 44,000VT per day. At Port Vila's Sportsmen's Hotel there's an ATM that dispenses Australian dollars, which you can then change at the bar (or a bank) at a (supposedly) favourable rate.
Take plenty of vatu everywhere outside Port Vila and Luganville as there are only a handful of NBV banks that change foreign currencies; additionally, hours are limited, queues are long and banks may run low on cash. There are plenty of tales of travellers running out of cash on Vanuatu’s islands. In remote areas it's useful to have coins and smaller-denomination notes.
The major credit cards are accepted by hotels, car-rental agencies, airline offices, most of the tourist-friendly shops and restaurants in Port Vila and, to a lesser extent, in Luganville. You can’t use credit cards outside these two towns and Tanna’s main resorts. The standard surcharge is 4% to 5% but this can still work out cheaper than ATM fees.
For current exchange rates see www.xe.com.
ANZ, Westpac and NBV all exchange major foreign currencies, including Australian and New Zealand dollars. Main offices are in Port Vila; branches are in Luganville on Santo. The NBV also has branches on major islands, including Lakatoro (Malekula), Lenakel (Tanna) and Pango (Pentecost), but these shouldn't be relied upon.
There are branches of Goodies Money Exchange in Port Vila, which offer good rates.
In kastom terms, tipping is an obligation that the receiver must return so, to avoid embarrassment, keep your ‘tip’ to a smile of thanks. Restaurant staff in Port Vila are happy to accept a tip, though.
Don't bother. Travellers cheques can only be changed in Port Vila and Luganville.